Study of a terahertz folded waveguide oscillator with sheet electron beam

Abstract

High power vacuum electronic devices of the millimeter wave to terahertz regime are attracting extensive interest due to their potential applications in science and technologies. In this paper, a novel sheet beam (SB) folded waveguide (FWG) slow-wave structure (SWS) is applied and studied for enhanced output power of oscillators. Through the analysis of high-frequency characteristics of the SB FWG-SWS, the selection of an appropriate beam–wave interaction point on the dispersion curve and beam position is determined for an SB folded waveguide oscillator (FWO) operating near the 2π stopband point. The fundamental mode operation of the SB FWO was verified by the particle-in-cell simulation results, which also indicate that the SB FWO exhibits a better outstanding performance (84.6 W with a beam voltage and current of 25.1 kV and 200 mA, respectively) than the conventional circular beam FWO. The transmission stability of the SB was analyzed by observing the interception beam current in the FWO. The voltage and frequency tuning performance of the SB FWO were discussed in combination with clutter suppression. A preliminary experiment was conducted by fabricating a 220 GHz SB FWG-SWS and measuring the S parameter.

Performance Evaluation and Experimental Study of a 0.34-THz Folded Waveguide Sheet Beam BWO

“…Because of the periodic design of the structure, numerous spatial harmonics become enabled. The phase shift of the mth spatial harmonics is given by [1]; Fig. 1: The vacuum model of a unit cell of the FWG SWS…”

“…where ω represents the angular frequency measured in radians, and k stands for the wave number along the axis of the curved waveguide. From the standpoint of beam-wave interaction, the beam observes the phaseshift from one gap to the next as given below [1]:…”

“…Terahertz (THz) waves encompass electromagnetic frequencies ranging from 0.1 THz to 30 THz. Contemporary THz technology serves essential roles in advanced satellite communication systems designed for high-speed data transmission, medical imaging, non-destructive testing, plasma diagnostics, particle accelerators, environmental sensing, quality control in manufacturing, material characterization, etc [1]. The researchers have been putting enormous efforts into the development of efficient, compact, coherent, reliable, frequency agile, powerful, and cheaper THz devices [2].…”

“…Electrical breakdown in the SWS may happen due to increased voltage of the beam beyond a certain level. Sheet beams handle this problem by spatially distributing the beam in one direction [1]. The sheet beam has been used in many THz vacuum electron devices but rarely in FWG SWS.…”

“…Anurag Srivastava et al [10] studied the electrical design of a 0.22 THz circular beam FWG BWO and fabricated the SWS using multi-step photolithography and etching processes in 2019. Fengying Lu et al [1] presented a 0.22 THz sheet beam FWG oscillator and compared its performance with a circular beam oscillator.…”